CVE-2023-52733

In the Linux kernel, the following vulnerability has been resolved:
s390/decompressor: specify __decompress() buf len to avoid overflow
Historically calls to __decompress() didn’t specify “out_len” parameter on
many architectures including s390, expecting that no writes beyond
uncompressed kernel image are performed. This has changed since commit
2aa14b1ab2c4 (“zstd: import usptream v1.5.2”) which includes zstd library
commit 6a7ede3dfccb (“Reduce size of dctx by reutilizing dst buffer
(#2751)”). Now zstd decompression code might store literal buffer in the
unwritten portion of the destination buffer. Since “out_len” is not set, it
is considered to be unlimited and hence free to use for optimization needs.
On s390 this might corrupt initrd or ipl report which are often placed
right after the decompressor buffer. Luckily the size of uncompressed
kernel image is already known to the decompressor, so to avoid the problem
simply specify it in the “out_len” parameter.